Gliederung

Background: After the first SARS outbreak in Early 2003, a re-emergent case was reported in Guangdong province in late 2003. However, compared to the previous cases, quite different clinical, epidemiological and serological features was observed from it. To make clear the differences between the re-emergent case and the ones occurring in the first outbreak, the genes of SARS-CoV spike protein from different sources were sequenced and analyzed.

Methods: To amplify and sequence genes coding the SARS-CoV spike protein, 8 pairs of primer were designed. The oropharyngeal swab sample collected from the re-emergent case and 3 strains of SARS-CoV isolated in Guangdong province during the first outbreak, were selected to extract RNA. Subsequently, amplifying and sequencing were proceeded. The sequencing results and other 13 sequences of SARS-CoV spike protein genes from GenBank were compared by personal computer.

Results: With the specific primers , fragments of 500-700 bases in length were obtained. purified and then used for sequencing. After assembling the raw sequences, a 3768nt sequence of complete spike protein gene was obtained from each sample, which codes 1255 amino acid. The multiple alignment showed that the homology of nucleotide and amino acid between the amplified spike protein genes and previously known coronaviruses were 99.3-100% and 98.4-99.9%. The phylogenetic analyses of these nucleotide sequences showed that the SARS-CoV of newly occured case and the SARS-like CoV of Himalayan palm civet fall into the same cluster, that showed the later might be the one of the originates of SARS; And a molecular evolution trends can be observed, through the strain associated with the re-emergent case and Himalayan palm civet strains which mutated into the late strains causing the SARS outbreaks all over the world in 2003.

Conclusions: The coronavirus which caused SARS in human probably was closely related to the coronavirus source from the Himalayan palm civet. Variation of the amino acid residue in the spike protein played an important role in the different biologic characters of SARS-CoV.